Induction-generator.



E. F. W. ALBXANDBRSON.

INDUCTION GENERATOR.

APPLICATION FILED AUG.3,A1907.

920,809. PatentedMay4,19o9.

)2%,70 Y Ernst F`. W. ff lexanderson,

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s-TATEs f PATnNir onirica;

nniisr r. w. ALiiirA'Nnnnsoir,4 orscnniincriinr, NEW `ironic,LAssieNoR To GENERAL .A .l y frRiccoMPANnA ooRPonATioN or NEW YoRK. i i

' Ne. 920,805. i

. concern:

'Be itknownt'hatfL ERNST F. W. ALEXAN-- I f mnUcTIoNGENnRAToR.

nERsoN', a 'citizen of theUnited. States, residing atSchenectady, county of Schenectady, State of lYew York, have invented-certain ynewaifiduseful'Improvements in Induction- Generatoraof which the following is a specification I l Bilyinvention relates to induction generators-designed to run at double synchronous speed. `lfhesle machines have both members provic'lfed with distributing windings somewhat likethe primary winding of an induetion motor, and in loperation both members are lconnected in parallel with the load-c'iicuit. Suchmachines possessan advantage, as compared with ordinary synchronous al- -ternatorswhen turbines orothe'i" hi hs eed ,i prime-movers, are used, and when low-freuencv currentsare desired since for a given frequency, aiidjliiumber of poles the induction generatcroperates at `twice the speed of the synchronous' generator, so that more efficient operation of the turbine is obtained. l The o hject Aof. my invention is to provide a novel method ofputting such machines into service, and asimple and eiiective arrange' mentfor facilitating starting the machines in accordance with .that method.

Indnctionniaclnnes require a synchronous ymachine for'iurnishing their exciting current '4 andiiring' the frequency. flfitne synchro- Aduction generator at starting asa synchro nous machine with direct-.current excitatlonand half its normal number of poles, syn-` nous exciter is 4mounted on the saine shaft with the induction generator, proper phase relations between"the two are fixed by the vmecl'ianical connection between them, and

there is .no difficulty in synchronizing thev induction lgeneratorl with other machines, or

with theload-circuit, since it may be fully excited .before throwing it into parallel with other machines. it is not always convenient, however, to mount the exciter on the same shaft with the induction generator, and then diiiiculties arise in connectingthe inachine to the bus-bars, since until it is connected to the bus-bars, it is not excited, and consequently when first thrown onto the busbars in parallel with other machines, it acts as a short-circuit on the bus-bars.

My invention consists in connecting the iii- 'chronizing it when so connected with the bussbars, Yand' then connecting it to the bus- Specication of Letters Patent.

Patnteanye, 1909;

' Application ined Auguste, 1907. serial No. 386,931.

I bars'with its normal numberoi'poles. I lf-the starting and running connections are' properly made with respec-t to each other, the induction generator acts like 'a properly syn chronized synchronous machine when thrown onto the bur-bars. For facilitating' this method of starting the generator l provide it, in addition to its main winding,'with an aux iliary'` winding on leach member of. half the number of poles of themain windings; nel

of these windings at starting is excited by direct-current, and the otherl is. synchronized with the bus-bars. i y

My invention will best be understoodby reference t0 the accompanying drawing, which shows diagrammatically an induction ings aand b are placed on the stator-androtor, respectively, winding a being a threephase winding, and the Winding adar t'e'djgenerator arranged to be thrown into circuit to be supplied'vm'th direct current. Co lec'f".v

tor-rings C1 to C4 are' providedfor the rotor, f

windings B and the main windingB being connected to collector-rings C2, C? 'and C4, and the auxiliary winding b tothe 'collect'o'rf rings C1 and C".

D represents the prime mover 'for the generator, whichv I have indicated diagram?.

matically as a steam turbine.

E represents thearmaturewinding ofthe synchronous machine, which serves as the exciter, and F is the field winding of this machine.

G represents a turbine the exciter. H represents a source of direct-current elicitation, which isarranged Ito be'connected through the switch h to the field windingv-y of the synchronous exciter. l

I represents a switch by means of which the armature winding E of the synchronous exciter is connected to the bus-bars J.

K represents a controlling switch for the induction generator having two` ositions, for starting and running respective y.

. 'Lrepresentsa lamp or other suitable'syn-A chronous indicator supplied 'from .a transformer M connected in paraliel with one hase of-.the bus-ba'rs, andthe transformer i I1 connected. in parallel with one phase of the auxiliary stator windinga.'

Th mated rsa1-ting the induction' machinev-'isaslfollowsz The synchronous ex-Y citer isi-started andswit'chh-,is-closed so as to excltethe field. jSWitch I isciosed sofas .5 to connect the armature ofthe exciter-to lthe Abus-bars; "If-other machines are-connected. to the bus bars', the fexc'iter issynchronized' therewith,*inthe usual manner; before switch LI is closed.. vThe induction generator is then li'startedfandswitch his closed'. Thisconnects the direct-current exciter to 4the co11ecto1ri'ngs'1C1 and C4, thereby supplyingv direct-current excitation toy the auxiliary uotor'winding b. y If the turbineBis run.

15 at lproper speed, a voltage is induced at the terminals of. vauxiliary stator winding "a approximately in synchronism with the By' means of the syn#l bus-bars. Consequently, if vthe switch K isv .thrown'quickly from its starting to its runl 3a ning position, so as to cut out the auxiiiary ,Winch Us and to connect windings A and B.

in para el to` the bus-bai's, the generator is thus thrown into circuit as an induction machine without producing a disturbingefect upon the bus-bar voltages.A i Y y I do not desire to limitl i yself to vthe particular construction and arrangement of parts'here shown, but aim in the appended i claims-to cover all modifications which are Within the scope of my invention;

What I claim as new, and desire to secure by Letters Patent of the United States, is,

1, The meth'pd of putting into circuit anv induction generator designed to run at double synchronous speed, which consists in connecting the generator as a synchronous bus-bars.

'machine 'with directLcurrent excitation and 'half its normal number of cles, synchronize ing with the bus-bars., an then connecting it -to the bus-bars as an induction'machine 'with its normal number of poles.

,l The method of putting into circuit an induction generator designedto run at double synchronus speed and having main windings and auxiliarywindings on .both

members,the auxiliary windings 'havin half the number-oi 'poles of the main win ings, f

which consists. in supplying direct-current to one auxiliary winding and synchronizing the other with the bus-bars, and then cutting the' auxiliary windings out of circuit and connesting both main windings in parallel to the 3. -An induction-generator designed to run at double synchronous speed having polyphase main windingson both members and 'an auxiliary winding oneachmember of half the number of poles of the main windings, oneiauxiliary winding having polyphase connections and the other' being adapted to be supplied vth direct current.-

4. An induction generator designed to run at double synchronous s eed having polyphase main windings on oth members and an auxiliary winding on each member of half the number of poles of the main windings, 'a source of direct eur1ient, bus-bars, means for connecting one auxiliary winding to said source, means for synchronizing the other auxiliary winding with the bus-bars, and means for connecting the main windings in parallel to the bus-bars.

5. An induction generator designed to 'run at double synchronous i speed, bus-hars, means'for connecting said generator for half its normal number oi" poles and'for supplying direct-current to one member of the generator, means for synchronizing said generator when so connected, and means for connect ing both members with their normal number oi' oies in parallel to the bus-bars.

n witness whereof, I have hereunto set my hand this 2nd day of August, 1907.`

i ERNST F. W. ALEXANDERSON. Witnesses:

BENJAMIN B. HULL,

HELEN Onronn. 

